Shorah
I would like to ask for your understanding, for any errors I have done in this document.
This is a short summary of Myst Universe history (lore) (made by me) with hope it will help you understand better the back-story of this place and also to answer questions that you have like (e.x why the Bahro stones are appearing and disappearing, or what is Uru Ages beyond Myst, the "To D 'ni, and the Path of the Shell, Uru Complete Chronicles, what is Mystonline ).
Of course it will not be clever for me to believe that I will cover everything because neither I know everything nor I am a writer.
The reason that I make this effort is because I was online between 2006-2008, I was the only lucky Greek explorer online and I learned a lot of things from other explorers that time (e.x bahroglyphs, lore etc).
For any corrections please reply. Also if you can do a better English translation please pm me and I will update this message if I agree.
This is the English translated post I made in Greek subforum.
Dimitrios

207 BE
7863 BC
All (known history) began with the birth of Ri 'neref in the Age of Garternay (which means Root of the Great Tree), where the Ronay people (the ancestors of D’ni) lived (they named themselves D 'ni when they link in Earth).
59 BE
7715 BC
It became publically known that Gartenay Age will be destroyed in a few years because of its sun destruction. They were given assurances that the population will travel in a stable Age with the name of Terahnee. Ri 'neref however, had written a book with which it could link to Earth (under Mexico dessert). He asked, from the King, the authorisation to do this, to link to Earth, with certain thousands of Ronay that wanted to follow. The King gave the approval and thus certain thousands Ronay, that were named D 'ni (which means “new start”), linked in the cave (the one that we call Cavern) in which they found the Au 'gera (the name of city in which we explore today).
0 DE
7656 BC
D’ni people construct the Great Zero .>(a machine that is connected with KI’s and gives us the coordinates in the Cavern. The line that has angle or corner coordinate, 0 (zero) shows us the magnetic north. In some Ages (it was priority to manufactured such machines in all the Ages) line 0 shows a certain other important landmark than magnetic north.
1 DE
7655 BC
The Ri'neref leads the group of his supporters to the Cavern and becomes the first King of D 'ni.

From the year 7656 BC up to roughly 1824 BC the following historical events happened:
18 Guilds are created and between them, the Guild of Writers.
The following buildings constructed and the following events happened:
1. The Yahvo Temple (Atrus = Yahvo)

2. An air ventilation system.(a small group from D 'ni escapes to the surface of Earth!!

3. The Arch of Great King (Great Arch or Arch of the King or Kerath 's Arch ) in order for the prophesy to be fulfilled (at the arrival, the Great King to pass under it).From that time all Kings of D’ni during their coronation passed under the Arch.

4. The Temple of Great King that was renamed later the Tomb of the Great King.

5. The war of Pendo Age (Pendo War).
1376 DE
6280 BC

6. The coronation of Great King (Great King Ahlsendar) after his victory in the Pendo war. He was born according to rumours (and prophesy) during his mother’s escape, at the exact moment her boat passed under the Great Arch. During his return, in order to free the city from D’ni enemies, he passed with a boat under the Arch, fulfilling the prophecy. When later the Mekarr a son of Pendo war leaders, killed his wife and his son, the Great King Ahlsendar ordered the soldiers to sent a virus to Pendo Age, a virus which was exceptionally lethal. When unfortunately the virus expanded also in other D 'ni Ages he admitted that he was the one that gave the command, asking from his people to prison and sealed him inside the temple of Great King. He gave also the order to D’ni never to unseal the door. Together with him, he took also many Descriptive books with various polluted Ages.

7. The Temple was named Tomb of Great King.

8. Temple of Tree was constructed.
1999 DE
5657 BC

9. The Tomb of Great King unsealed from Jolatha, who took various books in the Temple of the Tree, and died a few years later (from an evolved virus of King Ahlsendar). The Temple with the books was sealed again.
Even if Jolatha claimed that she saw the corpse of the King, bringing with her a piece of his clothes as a proof, it hadn’t been widely acceptable that the King truly died.
Many D 'ni (included me ) they believed that their King was alive and that he will return again. Also rumors existed that, Great King Ahlsendar was seen before his imprisonment to “ link ” not only without book but also in various places inside the same Age, something that only Yeesha (daughter of Atrus) accomplished a lot of years later.
2262 DE
5394 BC

10. The lost books of Birenni discovered and the illness (of the evolved virus) cured leaving the number of D 'ni population about a quarter less.
4500 DE
3156 BC

11. A collection of prophecies with the name “ Words ” was written from the Watcher. (see Myslore for more). Those prophecies are the six books we found in our relto in the offline version of URU (The path of the Shell) and in MOULagain in Watchers pub.

9312 DE
1657 AD

12. Atrius (no the Atrus) was born , the grandfather of Atrus who married years later Ti’ana). Ti’ana was the first human, from the surface, that discovered the D’ni. (The Book of Ti'ana is the first chronologically in Myst lore),(you can find it in MystReader with the other 2).
An outsider to be accepted by D 'ni was not at all easy.
Atrius and Ti’ana gave birth to Gehn.
9338 DE
1683 AD
13. The construction of Great Shaft begun. The Great Shaft ( regarotiwa[?] (regahrotiwah)) is a unique construction of the D'ni people built to connect their caverns to the surface, a controversial project some consider the beginning of the end of the D'ni. It was designed to speed up the tunneling to the surface. It consists mainly of a vertical tube, about 3 miles in length, with circular stairs as well as elevators to transport people up and down. We can see the floor of Great Shaft from Descent (there we link from a bahro stone).We can walk on the floor (and not only) in Myst 5 “ End of Ages ”.

9400 DE
1745 AD

14. The fall of D 'ni civilization. Veovis and A 'gaeris cause a big explosion and they manage to expand a deadly virus (with the help of ventilation system), in a form of black cloud. The black cloud killed everything, included lake algae which we, nowadays feed in order to help them produce more light in Cavern, with the pellets we drop.
Ti’ana and his child Gehn go up to the Cleft (somewhere in deserted New Mexico USA) via the passage from which she came down to D’ni and they are saved from certain death.

15. Gehn abandon Cleft (accusing Ti’ana that she was responsible for the fall) and discovers a race called Amad (on the surface), that had, from what it appears, the holographic projection technology. There is theory that Amad once had come to contact with the D 'ni that were escaped from Cavern firstly when they manufactured the ventilation system and secondly when they manufactured Great Shaft.
He met Keta there and he married her. They gave birth to a son, Atrus!!!
However Keta had complications during her pregnancy and died in Cleft where Gehn brought her for Ti’ana to help.
Gehn accuses one more time his mother Ti’ana and abandon her and his child, going down in Cavern in order to study alone D'ni civilization.
That is the moment Book of Atrus starts.
I would like here to say that Ti’ana trained Atrus with the question (what do you see), avoiding to answer directly his questions, educating him to discover, to observe and to comprehend what he sees.
9417 DE
1762 AD

Gehn started to write the book of Age “5” (Riven). He believes that he creates the Age (like a Atrus) writing the book . Gehn manipulate and terrorise the people live there and he force them to worship him as Atrus! The punishment was the death in the teeth of Wahrk. Wahrk is a marine-dwelling creature found in the waters of Riven. Presumably carnivorous, the wahrk resembles a large, tusked whale and can be viewed, up close and rather irritated, in an underground chamber on Survey Island.
While the collapse of Riven also implies the extinction of the wahrk as a species, at least one wahrk did make it through the Star Fissure (and presumably died soon after), as evidenced by a skeleton not far from the Cleft in New Mexico.(Mystlore)

9425 DE
1770 AD
Gehn takes, using violence, Atrus with him in the Cavern. Atrus meet Katran (Catherine) in Riven and falls in love.
9429 DE
1774 AD

Atrus, Anna and Catherine trap Gehn in the Age Riven. They move to live in Myst Island.
9431 DE
1776 AD
Atrus married Catherine and give birth to 2 children, Achenar and Sirrus.
9438 DE
1783 AD

Ti’ana dies in Myst island (you can find her grave in RealMyst).
9461 DE
1806 AD

At that point the events of Myst Game starts (for spoilers reasons I can only say this: play RealMyst!!).
9462 DE
1807 AD
Riven Game. (the best of the bests)
Atrus was freed from the stranger (we play the games as stranger ).Catherine was saved also. Gehn is trapped in a Prison book (special book that resembles a linking book)
9468 DE
1813 AD
Book of D'ni
Atrus start to search for D’ni survivors and he find many in various Ages.
He unseals Temple of Great King and he discovers a crypt with a book in it. With the use of that book he links to Terahnee where he discovers the survivors from Gartenay.
9470 DE
1815 AD
Atrus completes the book of Age Releeshahn and D'ni survivors linked there for a new start. Atrus build Tomahna (a place near Cleft) and moves there with Catherine where they give birth to Yeesha.
9471 DE
1816 AD
Exile game (Myst 3 Exile).
Saavedro steals the book of Releeshahn and a stranger (you) help Atrus to take it back.
9475 DE
1820 AD
Atrus and Catherine begin to visit their sons.( Spoilers again)
9479 DE
1824 AD
Atrus and Yeesha start to visit Serenia (Age).
Myst 4: Revelations (Game)
After short while Myst 4 events started.
After the end of Myst 4 Yeesha begins to learn more for the art of writing (Art of Writing).She met a D'ni survivor (Calam) with whom they become inseparable and they both learn the one from another. Yeesha follows mostly the sentiment, as her grand mother and her mother did, while Calam because of the conservative way that learned the art (he was member of Guild of Writers), had more limits but also logic.
Certain years later they met an unknown (until today) D’ni survivor (also known as "the Black Book". (Bahroglyphs in Eder Kemo)
When Calam was killed, when he battle to protect Yeesha from the attack of "The Black Book ", Yeesha, in a explosion of anger, killed him.
Yeesha start accusing herself for the death of Calam, but also she continues to learn more for the Art .
She made contact and lived with the Bahros (she learned also their language)
9642 DE
1987 AD
John Loftin the father of Jeff Zandi ( the fat guy near Cleft) and the owner of the land where Cleft is, discovers the Cavern.
During next years, Dr Watson visits the Cavern followed by Cyan (Rand Miller, Robyn Miller) and the creation of Myst (Game) begun.
Riven, Exile, Revelations and the End of Ages are following. (OCC= out of cavern)
DRC council is founded from Dr Watson after its disagreement with Zandi with purpose to restore Au’gera. D'ni Restoration Council (DRC).

9657 DE
2002 AD
First explorers go down to the city (Au'gera).
Around September of 2002, Phil Henderson went missing through a Linking tunnel in Eder Kemo. Upon returning after a year, Phil spoke with people about the teachings of Yeesha. However around Christmas of 2003, he was believed killed by a cave-in while in a place not open for the general public. The DRC, who had the area excavated, were unable to find his body, although they did find his KI which he had taken off before the cave-in. (Read books in Sharpers office and in Descent).
I am not sure but I believe the first explorers they didn’t have a relto book because Yeesha’s journey was not available at that time (please correct me).
9658 DE
2003 AD
More explorers from the surface with the help of Zandi (without authorisation from the DRC go down for first time in Cavern.
(Uru Ages Beyond Myst)
After Phil’s “death” many explorers (Sharper and Dr Watson included) decide to follow Yeesha’s journal , which Phil insisted and for which DRC was negative for safety reasons (role-playing with simultaneous story unfolding, impressive e?). Relto book becomes a gift for whoever finish Yeesha’s journal.
9659 DE
2004 AD
D’ni restoration effort stops and online Uru Ages beyond Myst as result it stops also (or the opposite depends how you see things IC (in cavern) or OCC) .
Cyan release the offline add-on : 1) “ to D 'ni ” and 2) “ The Path of the shell ”.
All three together became Uru Ages beyond Myst: Complete Chronicles.
9660 DE
2005 AD
Myst 5: End of Ages. (Game).
In this game we play also as a Stranger (not the same protagonist from Myst 1,2,3,4) and we release the bahros.

9661 DE
2006 AD
DRC returns in the Cavern.

9662 DE
2007 AD
Mystonline ( Urulive) come back online available through Gametap.
Cate Alexander reveals new sources for financing restoration project.
First spark (these blue balls) and first bahro stone are discovered!!!! Later we learn that bahros bring and take the bahro stones. Yeesha starts to influence the restoration in a different way DRC wanted to.
Jalak, Minkata and the Pod Ages Eder Tsogal and Eder Delin released and Cyan announces the 5 officially Guilds in which we can become members wearing the corresponding T-shirt.(Kirel)
Sharper reports that he discovers some slashed remains of animals in Negilahn..
Sharper speaks for dramatic reduction of population of animals there and go again taking all the precautions and his gun. .
Wheely Engberg (daughter of Michael Enberg, member of DRC) and Rosette Taylor are trapped during a marker game in an internal cave in Au’gera. Shocking rescue efforts are following from the DRC (strong sentiments, incredible role-playing) during that episode. (Almost every month we had an episode).
Rosette is killed by a rock at her entrapment there, while Wheely reports that she is hearing curious noises and see eyes looking at her.
After few hours she loses her senses again and just before her rescue, we understand that she was trapped in a bahro cave (not those that we go) BUT in a different one, with no light and with the symbol %, which we also found later in Minkata. I believe it symbolizes the separation from good and the evil.
The very moment of her rescue she was killed by a bahro.
Her father Michael Enberg (member of DRC) leaves from Cavern for ever (?).
(There is also roleplaying inside DRC of council).
Nick White is expelled from the DRC because of the revelations he makes, to the explorers, for several secret books that he had knowledge about and also because of his sentimental entanglement with a female explorer.
Sharper comes in the city and announces that he was rescued literally the last moment from a certain death by a flying and exceptionally fast bahro. He said also that bahros are in civil war and some of them sacrifice their life to save him. Minkata and the Great Zero become available.
DRC on 27 June 2007 installs a monument (memorial) in the entry of Kahlo Pub. The names written on the memorial are the names of various explorers that left from life (the real life) all these years. (Also we can see Phil Henderson (Phend), Rosette and Wheely names on it)
Phil Hendrson reappeared and speaks for bahro civil war.
Appearances of bahros in the city started and some explorers were lucky enough to “speak" with them (the communication was done using /me ..bla bla bla).(Tip , to speak with them always sit and say (/me … blablabla) something good to them. Its a kind of thought communication . YES it happened to me )
The number of appearances increases in the city but also in other Ages (like Relto. There is a youtube video) and our safety concerns grow bigger and bigger (episode titled Exodus).
Hundreds of Bahros flying above the City and Yeesha appeared in K'veer.
She explains to us that Bahros are free henceforth (after the events of Myst 5) and that the freedom brings the choice and the choice the responsibility.
Thus some bahros choose to revenge us but most from them choose to protect us. It explains that she will attract them to other Ages gaining time for us to make a home but someday she will return and also the bahros.
Finally we had learned that Dr Watson was the Stranger in Myst 5 and that he freed the bahros. He insists, Guilds to be created by us, in order to make a home.
9663 DE
2008 AD
Mystonline closes.
9664 DE
2009 AD
Cyan announces that after it took the rights back for Mystonline, they will make the game open source in order whoever wants to create Ages, to join this new Age to Mystonline later in time.
9665 DE
2010 AD
Some members of DRC report for strange activity in their sensors in Cavern that is recorded by their instruments.
Some of them goes down and discovers that many explorers are returning.
Mystonline is back online!!
The End has not yet been written………

Finally I found the last speech of Yeesha in the Kveer:
"I will have words. Destruction is almost upon us. They are here. Fighting in war. Freed from their prison, the Bahro choose their way now; good and evil stand before them. No longer are they slaves to the tablet, no longer is their destiny locked to the wishes of others. No longer is their freedom captive. They are powerful and with freedom, some are dangerous.
Most of the Bahro are friends. They stand with us, protecting us from the evil that surrounds you almost constantly. They sacrifice for you. They battle an die for this cavern. They battle and die for the Ages, and your comfort. They fight for the D'ni as well. They watch over us all.

But there are those who have not chosen to side with you, with the D'ni, or with good. They seek revenge for the evil done to them. Revenge is their excuse but freedom is their cause. They are able to make the choice and they bask in such opportunity to do as they please. With freedom comes choice and with choice comes evil, as well as good.

Their leader can be seen clearly. He is missing a large patch of skin on his shoulder - taken from him in the tortuous lab of Esher. Because of that, I will draw them away. Away from the cavern. Away from you. I do not know how long they will seek what I carry. It could be only days, it could be months.

Destruction is coming. It is almost here. I will delay it as long as I can but, in the meantime, you must find a way. You must make a home. Destruction will be here soon. I will try to return and help you in the future. If things go well, I will offer you my aid. If things do not, you must find a way on your own. Regardless, you must be ready.

Destruction will come... soon or later. When it does, you must have a way. You must make a home. I will do all that I can in the meantime.

I must leave now.

Goodbye. "

Sources Mystlore and ….me 

_________________With freedom comes choice and with choice great responsibility.
and pssst.. the Great King Ahlsendar is alive Dimitrios Ki # 35506
Greece Ki # 117119

Dr Joseph feel free to post anything you believe that is missing and i will add it in my first post.Maybe its time for someone (i hope not me because of the language) to write the complete history of this place in one book.
Lets do the start, in order to help new adventurers and ourselves to understand more clearly what is happening.
Thank you very much in advance.

_________________With freedom comes choice and with choice great responsibility.
and pssst.. the Great King Ahlsendar is alive Dimitrios Ki # 35506
Greece Ki # 117119